The present invention relates to electronic monitor devices intended for disposable use in packaging. Such devices may monitor temperature, humidity, pressure, acceleration, and other parameters which may affect transported goods.
Temperature monitors are important in any industry involving products that are temperature sensitive. This includes such broad categories as food and beverages, medical and pharmaceuticals, biologicals, and industrial chemicals and adhesives. In addition to producers within these industries, monitoring the environment of products is important to distributors, suppliers, storage facilities, and large service providers such as hospitals, the military, and large restaurant chains.
Within each of these industries there are a variety of reasons for using an environment monitoring device. For example, such monitors may be used as an aid in controlling product quality, to monitor the performance of shippers, to minimize product loss due to temperature exposure, and to aid in identifying responsible parties in instances of product loss. It is known that substantial amounts of fresh produce are lost each year in the transportation phase of distribution, largely due to temperature variations during transport.
While temperature is a significant cause of damage to transported goods, it is not the only cause of damage. Other identified causes include improperly stacked boxes resulting in shock to the packaging, improper packaging materials leading to shatter, product damage during loading, and moisture loss. Improper handling often leads to in-transit vibration which may aggravate problems started at the packing house. It may be important, in a given field, to monitor any one or all of these factors to control shipping loss to goods.
Over the years, commercially available products have been developed to monitor temperature for transportation of goods. These products often include strip recorders that produce hard copy output. The classic strip recorder recorded temperature on a revolving drum, the speed of which could be altered depending upon the amount of time that needed to be recorded. Modern strip recorders are more likely to be digital and will store the information as it is recorded for later retrieval. For those devices, a specialized reader or a computer with a graphics capability printer is required to read out the recorded information. One commercially available product incorporating such a strip recorder is manufactured by Ryan Instruments, Redmond, Wash.
The Ryan monitors are relatively large, and are intended to be installed either in the environment of a transportation vehicle, or in large containers containing the temperature-sensitive goods. The Ryan monitors record temperatures in memory, and the recorded information is accessible by an external access device, such as a computer, by printout using a bimetal coil recorder, or by visual LCD display. Various models of Ryan monitors test for humidity, with similar forms of data output.
Control One, Inc., Stamford, Conn., manufactures a line of time and temperature monitors. These devices have internal recorders utilizing stainless steel or Teflon probes. Temperature readings may be taken as often as every four seconds, or as infrequently as once every 72 hours. These devices are generally housed in a closed housing unit which can be selectively turned on and off. In many shipping situations it is undesirable to enable the user to turn off an activated system, since it would facilitate fraudulent readings.
Both the Ryan and the Control One devices are pre-programmed by the manufacturer to read a broad range of temperatures, or an end-user specified range. Both manufacture devices which may be coupled to an external printing device, and some must be returned to the manufacturer for a secure parameter reading.
A third type of device is manufactured by 3M, St. Paul, Minn. These "product exposure indicators" give visual signals of temperature exposure. The devices are generally in the form of tags and labels which record the cumulative exposure time spent over certain temperatures. These indicators function by means of an irreversible physical change. If exposure occurs beyond a specific temperature level, these indicators detect and record the extended temperature elevation.
In an exemplary 3M device, each tag has a temperature set point, and visually indicates the temperature change by color change or indicator movement. Each tag has a series of viewing windows on the top surface, protected by a clear film overlay. When the activation temperature of the tag is exceeded, e.g., above 10.degree. C., a blue color appears in a window, and gradually moves across the tag windows with time. Movement of the color indicator is halted if temperature falls below the set point, and resumes again with temperature rise. The location of coloration shown through the viewing windows is a function of time and temperature. That is, a short period of exposure at a relatively high temperature will result in coloration comparable to a longer period of exposure at a lower temperature.
These types of devices do not enable long-term parameter monitoring against user-determined preselected parameters. It is important that the monitoring device be tamper-resistant, to prevent manipulation of the recorded readings. It is also desirable that the end-user be able immediately to take a reading of any temperature fluctuation. Cumulative measurements are not as useful as discrete event detection for those situations when short-term exposure to extreme temperatures is detrimental to the goods, such as pharmaceuticals or other biological materials.
Accordingly it is an object of the present invention to provide a relatively accurate, dynamic and inexpensive way to monitor the temperatures to which products are subjected during shipment.